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Method and apparatus for measuring distance using low clock rate signalMethod and apparatus for measuring distance using low clock rate signal description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20060214840, Method and apparatus for measuring distance using low clock rate signal. Brief Patent Description - Full Patent Description - Patent Application Claims
CROSS-REFERENCE TO RELATED APPLICATIONS [0001] This application claims the benefit under 35 U.S.C. .sctn. 119 (a) from Korean Patent Application No. 2005-24961 filed on Mar. 25, 2005 in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference. BACKGROUND OF THE INVENTION [0002] 1. Field of the Invention [0003] The present invention relates to a method of measuring a distance between two devices, and more particularly, to a method of improving precision of measuring a distance between two devices using a low clock rate signal. [0004] 2. Description of the Related Art [0005] In general, radio waves are used to measure a distance between devices A and B. FIG. 1 is a view illustrating a process of measuring a distance between devices A and B according to the prior art. The process of measuring the distance between the devices A and B according to the prior art will now be described with reference to FIG. 1. [0006] The device A transmits radio waves to the device B in operation S100 so as to measure a distance between device A and device B. In this case, the device A counts a clock of a clock signal having a uniform clock rate upon transmitting the radio waves. In general, the radio waves are transmitted at a light speed. The device B receives the radio waves and processes the radio waves in operation S102. In other words, the device B performs predetermined processing to re-transmit the radio waves to the device A. [0007] The device B transmits the radio waves having undergone the predetermined processing to the device A in operation S104. The device A stops counting the clock and calculates a count value in operation S106. The device A measures the distance from the device B using the count value. Here, the device A calculates the distance in consideration of a time required for transmission and reception of the radio waves after subtracting a time required for the predetermined processing at the device B therefrom. [0008] For example, if the clock frequency of the clock signal counted by the device A is 100 MHz, the radio wave moves 3 m for a clock of the clock signal. Thus, if the count value of the device A is "100," the distance between the devices A and B is 300 m. Also, if the clock frequency of the clock signal counted by the device A is 10 MHz, the radio wave moves 30 m for a clock of the clock signal. Thus, if the count value of the clock at the device A is "100," the distance between the devices A and B is 300 m. As described above, a movement distance of the radio wave for a clock varies with a clock frequency of a counted clock signal. An error in a measured distance depends on the clock frequency of the counted clock signal. As the clock frequency of the counted clock signal is high, the error in the measured distance is small. As the clock frequency of the counted clock signal is low, the error in the measured distance is large. In more detail, if the clock frequency of the counted signal is 100 MHz, the measured distance has an error of 3 m. However, if the clock frequency of the counted signal is 10 MHz, the measured distance has an error of 30 m. [0009] Accordingly, a high frequency clock signal may be used to reduce an error in the distance between the devices A and B. However, a high frequency clock signal generator generating a high frequency clock signal is more expensive and more difficult to be realized than a low frequency clock signal generator. Therefore, a method of improving precision of measuring a distance between devices using a low frequency clock signal is required. SUMMARY OF THE INVENTION [0010] Accordingly, the present general inventive concept has been made to address the above-mentioned and/or problems, and an aspect of the present general inventive concept is to provide a method of precisely measuring a distance between devices using a low frequency clock signal. [0011] Another aspect of the present general inventive concept is to provide a method of reducing cost for components necessary for measuring a distance. [0012] According to an aspect of the present invention, there is provided a method of measuring a distance of a device, including: transmitting radio waves and counting (N3) a number of clocks of a clock signal having a clock frequency b; if the radio waves are received, counting (N1) a number of clocks of a clock signal having a clock frequency a; if the signals having the clock frequencies a and b overlap with each other, stopping counting the numbers of the clocks of the clock signals having the clock frequencies a and b; and measuring the distance using the count values of the clock signals having the clock frequencies a and b. [0013] According to another aspect of the present invention, there is provided an apparatus for measuring a distance of a device, including: a third counter transmitting radio waves and counting (N3) a number of clocks of a clock signal having a clock frequency b; if the radio waves are received, a first counter counting (N1) a number of clocks of a clock signal having a clock frequency a; if the clock signals having the clock frequencies a and b overlap with each other, a controller instructing the third and first counters to stop counting the number of the clocks of the clock signals having the clock frequencies b and a; and a calculator calculating the distance using the count values of the third and first counters according to a control command of the controller. [0014] The present invention suggests a method of using two low frequency clock signals having clock frequencies with a difference to precisely measure a distance. BRIEF DESCRIPTION OF THE DRAWINGS [0015] The above aspects and features of the present invention will be more apparent by describing certain exemplary embodiments of the present invention with reference to the accompanying drawings, in which: [0016] FIG. 1 is a view illustrating a process of measuring a distance between devices according to the prior art; [0017] FIG. 2 is a block diagram of a device measuring a distance according to an exemplary embodiment of the present invention; [0018] FIG. 3 is a flowchart of a method of measuring a distance via a device according to an exemplary embodiment of the present invention; and [0019] FIG. 4 is a view illustrating counting operations of counters constituting a device according to an exemplary embodiment of the present invention. DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS Continue reading about Method and apparatus for measuring distance using low clock rate signal... 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